Blogs

Agility@Scale: Strategies for Scaling Agile Software Development

Scott is a Senior Consulting Partner of Scott W. Ambler and Associates, working with organizations around the world to help them to improve their software processes. He provides training, coaching, and mentoring in disciplined agile and lean strategies at both the project and organizational level. He is the founder of the Agile Modeling (AM), Agile Data (AD), Disciplined Agile Delivery (DAD), and Enterprise Unified Process (EUP) methodologies. Scott is the (co-)author of 19 books, including Disciplined Agile Delivery, Refactoring Databases, Agile Modeling, Agile Database Techniques, The Object Primer 3rd Edition, and The Enterprise Unified Process. Scott is a senior contributing editor with Dr. Dobb's Journal and his company home page is ScottWAmbler.com

Test-driven development (TDD) is a common agile programming technique which has both specification and validation aspects. With TDD, you specify your software in detail on a just-in-time (JIT) basis via executable tests that are run in a regression manner to confirm that the system works to your current understanding of what your stakeholders require.

TDD is the combination of test-first development (TFD) and refactoring. With TFD, you write a single test (at either the requirements level with customer/acceptance tests or the design level with developer tests) and then you write just enough software to fulfill that test. Refactoring is a technique where you make a small change to your existing code to improve its design without changing its semantics.

TDD offers several benefits:1. It enables you to take small, safe steps during development, increasing programmer productivity.2. It increases quality. Agile developers are doing more testing, and doing it more often, than ever before. We're also fixing the problems that we find right on the spot.3. It helps to push validation activities early in the lifecycle, decreasing the average cost to fix defects (which rises exponentially the longer it takes you to detect them).4. Through single sourcing information, by treating tests as both specifications and as tests, we reduce the work required, increasing productivity.5. We leave behind valuable, up-to-date, detailed specifications for the people who come after us. Have you ever met a maintenance programmer who wouldn't want a full regression test suite for the code that they're working with?

But TDD isn't perfect. Although TDD is great at specifying code at a fine-grain level, tests simply don't scale to address higher level business process and architectural issues. Agile Model Driven Development (AMDD) enables you to scale TDD through initial envisioning of the requirements and architecture as well as just-in-time (JIT) modeling at the beginning and during construction iterations. To scale requirements-level TDD, you must recognize that customer tests are very good at specifying the details, but not so good at providing overall context. High-level business process models, conceptual domain models, and use cases are good at doing so, and these work products are often created as part of your initial requirements envisioning and iteration modeling activities. Similarly, to scale design-level TDD you must recognize that developer tests are very finely grained but once again do not provide overall context. High-level architecture sketches created during envisioning activities help set your initial technical direction. During each construction iteration, you'll do more detailed design modeling to think through critical issues before you implement them via TDD.

You also need to scale the validation aspects of TDD. TDD is in effect an approach to confirmatory testing where you validate the system to the level of your understanding of the requirements. The fundamental challenge with confirmatory testing, and hence TDD, is that it assumes that stakeholders actually know and can describe their requirements. Therefore you need to add investigative testing practices which explore issues that your stakeholders may not have thought of, such as usability issues, system integration issues, production performance issues, security issues, and a multitude of others.

For further reading, I suggest:1. My article "Introduction to TFD/TDD" at http://www.agiledata.org/essays/tdd.html which overviews TDD.2. My February 2008 column in Dr. Dobb's Journal entitled "Scaling TDD" at http://www.ddj.com/architect/205207998 which explores this issue in detail. 3. Andrew Glover's article "In pursuit of code quality: Adventures in behavior-driven development" at http://www.ibm.com/developerworks/java/library/j-cq09187/ which describes a new-and-improved take on TDD called BDD.[Read More]

When it comes to testing on agile projects it is common practice for agile teams to adopt a "whole team testing" approach where the team itself does its own testing. To accomplish this agile teams will often embed testers in the development team. Programmers will work closely with the testers, often via non-solo development strategies such as pair programming, to pick up their valuable testing skills. The testers will in turn pick up new skills from the programmers, and in effect both groups will move away from being just specialists (testers or programmers) to being what's called generalizing specialists. Whole team testing can be very different from traditional approaches where programmers may do some testing, often unit testing of their own code, and then throw it over the wall to testers and quality assurance (QA) professionals for verification and validation.

The types of testing that the parallel independent test team performs may include:

Pre-production system integration testing. Does the solution work within your overall organizational ecosystem? Importantly, if this is one of several teams currently developing new solutions, does this team's solution work with what will be in production (including the work in progress of other teams) when they go to release? In mid-to-large organizations the only economical way to do this sort of testing is via an independent, centralized team.

Usability testing. Although it's possible to do usability testing on the development team, the reality is that usability testing is a specialized skill that few people have (although could pick up via non-solo development). Furthermore, particularly for solutions with many potential users, you may want to invest in a usability testing lab. This is a centralized resource, or an outsourced resource these days, which is shared across many teams.

Security testing. Security testing is also a specialized skill, albeit one well supported with sophisticated security testing tools such as the Rational Appscan suite which can be included in your continuous integration (CI) strategy. Many organizations will centralize their security testing efforts.

Exploratory testing. The fundamental goal of exploratory testing is to discover where the solution breaks, as opposed to confirmatory testing which focuses on showing that the solution conforms to the requirements (this is the type of testing the development team typically focuses on). Exploratory testing is also a skill, a good one which everyone should strive to pick up, but exploratory testers are often few in number in many organizations. So, to leverage their skills effectively you may want to have some of them on the independent test team while they mentor others while doing so.

Non-functional testing. Non-functional requirements have a tendency to fall through the cracks on some development teams. Knowing this the independent test team will often "test to the risk" and focus on non-functional issues.

And much more. The above points are just exemplars, not an exact list. Please follow some of the links above for greater detail.

I'd like to leave you with several important thoughts:

The developers still do the majority of the testing. Just because there's an independent test team it doesn't imply that they are the ones doing all the testing. In fact, nothing could be further from the truth. They should be doing the minority of the testing effort, albeit the more difficult forms of it.

An independent test team will support multiple dev teams. For example, a test team of 5-6 people could support several development teams totalling 70 to 80 people. I typically look for a 15:1 or 20:1 ratio of developers to independent testers, hopefully even higher than that.

You need to consider better tooling. Although the development team will still be using common agile testing tools such as the xUnit and FIT frameworks the independent test team (ITT) will need more sophisticated tooling. First, the ITT will need to be able to report defects back to the team easily. When the development team is using a Jazz-based tool such as Rational Team Concert (RTC) then this can easily be done using either RTC (the web interface may be sufficient) or another Jazz-enabled product such as Rational Quality Manager (RQM). Second, the ITT will likely need more sophisticated testing tools, such as Rational Appscan for static and dynamic security testing and Rational Performance Tester (RPT) for performance testing (just two of several software quality management tools you should consider).

Independent testing is economical. Although I listed several tools in my previous point (hey, I do work for a vendor after all) an "unfortunate" implication of my advice (unfortunate for IBM at least) is that you can reduce the number of licenses that you require and still get this critical testing done by centralizing their use.

It may be a bit more complicated in regulatory environments. In a strict regulatory environment the independent test team may need to repeat, or at least validate, the testing efforts of the development team. In regulatory environments my fundamental advice is always this -- Have practical people, including yourself, read and interpret the regulations. If you leave it to the bureaucrats you'll get a bureaucratic solution.

This is an important scaling technique. Parallel independent testing, when done in an agile manner, is an important technique which you should consider when scaling agile strategies to meet the uniques needs of the situation that you find yourself in.

Over the past few months I've had several people ask me whether it makes sense to offshore agile testing, and more importantly when it makes sense to do so. So I thought I would share my thoughts on the subject:

Focus on whole team testing. The basic strategy is that agile teams should strive to do as much, if not all, of the testing themselves. We call this whole team testing. For organizations new to agile this can be daunting because they may be organized in such a way that programmers write code and then hand it over to testers for validation and verification. The implication is that organizations will need to invest in their staff so that the programmers become more well rounded and pick up testing skills (we refer this as moving from being a specialist to a generalizing specialist).

Offshore entire development teams. A common strategy for organizing geographically distributed agile teams is to have whole teams at each location. For example, if your larger team is spread across three locations - Toronto, London, and Bangalore - then each team is responsible for implementing end to end functionality. With a component-based approach the Toronto team should be fully responsible for one or more subsystems, the London team responsible for one or more subsystems, and the Bangalore team responsible for one or more subsystems. With a feature-team approach the Toronto team would implement all of the functionality, end-to-end, for a feature regardless of which subsystems that functionality affects. Agile teams typically aren't organized by job function (e.g. analysis is done in London, design and coding in Toronto, testing in Bangalore) due to the overhead of handoffs between sites, the increased risk of miscommunication due to less effective ways of communicating information, and the increased complexity of managing the work.

Adopt independent testing at scale. You may choose, or be forced to have, an independent test team that focuses on some of the more complex forms of testing. The general idea is that this team works in parallel to other subteams and tests their working builds on a regular basis. Having said that, the vast majority of the testing effort should still be done in a whole team fashion. If your team is experiencing agile scaling factors such as domain complexity or technical complexity then you may find that it makes economic sense to have an independent test team focus on forms of testing that are difficult for the subteams to address, in particular pre-production system integration testing. If your team is in a regulatory domain where independent testing is required, then you're better off to "shift left" this effort with an independent test team to reduce both cost and risk.

Offshore independent testing carefully. I would offshore independent testing only to organizations that I have a very good, long-term relationship with that have proven that they can work in a disciplined agile manner. I would also want to ensure that they have actual experience with agile independent testing AND are staffing the team with people that have that experience. A clear sign that they don't understand what is required is if the independent testing team is asking for a detailed requirements specification, an indication that they're planning on doing confirmatory testing which is better suited for whole team testing. Furthermore, I would only do this if I don't have adequate staff to do so myself AND do not have time to build up my own independent test team.

I suspect that you're going to find yourself in serious trouble if:

You do not have successful experiences with agile delivery in simpler (e.g. non-offshoring) situations first. Walk before you try to run.

You think you can save money by having agile programming done in one location and agile testing in another (the coordination costs are going to be much larger than you think)

You're offshoring testing because you're new to agile (in this situation you don't have the experience to organize let alone govern the offshored activities)

You work with a service provider where you don't have a proven track record with them when it comes to agile development (a proven track record with traditional approaches is a good start but still very risky)

In short, it can make sense to offshore agile testing in a very narrow range of situations. Be very careful.

I recently wrote a detailed article about Large Agile Teams that was a detailed walkthrough of how to structure agile teams of various sizes. I suspect that this is the most comprehensive online discussion of this topic. The article addressed the following topics:

Organizing Agile Teams. The article starts with a summary of the results of some industry research that I've done regarding the size of agile teams, showing that agile techniques are in fact being successfully applied on a variety of team sizes. It then goes into detail describing the organization structure of agile teams at various sizes. The article starts with a discussion of small agile teams, covering the common rhetoric of how to organize such a team and then making observations about what actually happens in practice. It then walks through two approaches to organizing medium sized teams of 15 to 50 people - a structure for a single team and a structure for a team of teams. Finally, it walks through how to organize a large agile program of 50+ people, focusing a fair bit on the need for a leadership team to coordinate the overall activities within the program. This advice is similar to what is seen in the SAFe framework although proves to be a bit more flexible and pragmatic in practice.

Supporting Large Agile Teams. The leadership structure to support a large agile team is reasonably straightforward once you understand the issues that such a team faces. In this section the article overviews the need for three important sub teams within your overall leadership team: The Product Delivery Team, The Product Management Team, and The Architecture Team. It also describes the need for an optional Independent Testing/Integration Team, something misleadingly labeled an integration team in SAFe, that reflects some of the known agile testing and quality practices that I've been writing about for several years.

Organizing subteams. The article includes a detailed discussion for how to organize the work addressed by agile sub teams within a large agile program. These strategies include feature teams, component teams, and internal open source teams. As you would expect with the Disciplined Agile Delivery (DAD) framework, the article clearly summarizes the advantages and disadvantages of each approach on provides guidance for when (not) to apply each one. I suspect you'll find this portion of the article to be one of the most coherent discussions of the Feature vs. Component team debate.

Tailoring agile practices. The article provides a detailed overview of how the various DAD process goals are tailored to address the issues faced by large teams. This advice includes: Do a bit more up-front requirements exploration; Do a bit more up-front architectural modelling; Do a bit more initial planning; Adopt more sophisticated coordination activities; Adopt more sophisticated testing strategies; and Integrate regularly. My hope is that you find this part of the article very illuminating regarding how the DAD framework provides flexible and lightweight advice for tailoring your approach to address the context of the situation that you face.

Other Resources. The article ends with a collection of links to other resources on this topic.